What did charles darwin predict after observing the 11-inch long nectaries of the angraecum sesquipedale orchid in madagascar?

I believe the answer is: it can only be pollinated by one species of moth, reducing cross fertilization

Pollination on flowers occurs when the movement of insects that feed on the flowers' nectar cause the male and female genitalia of the flowers to interract with one another. The longer the nectaries, the less amount of insects able to reach the nectar. This would make the female and male genitalia of the flowers unable to itnerract with one another.